Judith Collins says parents of the kids allegedly sexually assaulted at a Labour Party youth event should have been told right away.

Four 16-year-olds were reportedly attacked and harassed by a 20-year-old man at a Young Labour summer camp in Waihi last month. Labour didn't inform the teenagers' parents.

General secretary Andrew Kirton told RNZ earlier this week they'd been advised that would "add more distress" for the victims, and MP Phil Twyford reiterated that view on The AM Show on Friday morning, saying they'd been told not to "widen the circle".

The Housing Minister admitted if it was one of his own children, he'd liked to have been told right away.

"It's not a good situation. We're not happy about it. I think we let these young people down," Mr Twyford told host Duncan Garner.

Judith Collins and Phil Twyford.
Photo credit: The AM Show

Ms Collins, appearing alongside Mr Twyford, said there should never have been any question about what parents would have wanted.

"I'd actually rip their throats out for doing that, if it was my kid, I really would. Obviously not physically, but you might as well. That's what I'd want to do.

"I cannot believe they'd sit there saying, 'Let's not widen the circle.' Why not? This is the culture of secrecy that actually breeds this sort of behaviour."

Though Labour leader and Prime Minister Jacinda Ardern says she knew nothing about the alleged attacks until questioned about it by media, Ms Collins said she was "really disappointed" in her handling of the controversy.

"She was one of the first people to come out and call out the Chiefs rugby team for their behaviour. She called out Kevin Robertson's comments on Saatchi and Saatchi. She called out Russell McVeagh. Andrew Little's been espousing all these things that they should be looking at in the legal profession. How about having a look in their own home at what's going on? It's not good enough."

Mr Robertson made headlines in 2016 when he said the lack of women in business leadership roles wasn't a problem. That same year, members of the Chiefs rugby team were accused of abusing strippers.

Labour has organised an independent inquiry into what happened in Waihi, and its response.

"We recognised that the situation was completely unsatisfactory," said Mr Twyford.

"Those members of the youth wing of the Labour Party should never have been put in a situation where they were organising events where alcohol was available where there were under-18s there. Putting them in that situation was unfair. The party let them down."

Young Labour won't be allowed to organise any parties anymore, he said.